1. Field of the Invention
The invention relates to a video data record/playback system including video cameras, monitor devices, recording devices, and the like.
2. Description of the Related Art
A video monitor system in which video pictures are taken by arranging video cameras at various locations in a factory or the like and in which the video pictures from all of the thus arranged video cameras can be seen intensively at the central monitor station are now, extensively employed. While conventional video recordings have been made mainly with analog signals, recent development in digital video technology increasingly encourages the use of digital signals, which in turn has made it possible to handle video/audio data directly as computer data.
FIG. 10 shows an example of such a video monitor system. In FIG. 10, reference numeral 1 denotes a video camera; 2, a video transmitting device; 3, a network; and 4, a monitor device. The video cameras 1 that are arranged at various locations are regularly send signals of video pictures taken by themselves to the video transmitting device 2.
Operation of the thus constructed system will be described. When the operator specifies a video transmitting device 2 through a monitor device 4, such specified video transmitting device 2 selects a video picture of a similarly specified single video camera 1, subjects the video picture to an analog-to-digital conversion process, subjects the converted digital video data to a data compression process, etc., and thereafter transfers the thus processed video data to the monitor device 4 regularly through the network. The monitor device 4 expands the compressed video data and plays back the expanded data on the screen thereof. It is in this way that a video picture of an arbitrarily selected video camera 1 can be displayed on the screen of a monitor device 4. By watching at a monitor device 4, a video picture of one of the video cameras arranged at various locations, while arbitrarily switching the video cameras, operations in a factory can be monitored as a whole. On the other hand, with respect to video picture recording, analog video picture recordings are usually made for each camera. In the example shown in FIG. 10, a recording device is arranged within a video camera 1 or a video transmitting device 2, and the recorded tape is seen off-line later. This is how the conventional video monitor system is operated.
As described above, in the conventional art, a recording device is arranged close to a video camera 1, the video data generating means, and makes a recording off-line. As a result, recording devices whose number is substantially equal to the number of video cameras 1 are required, which in turn makes the system expensive. In addition, in order to see recorded video pictures, the operator must later go to the place where the recording device is located and take a recording medium out of the recording device, which is cumbersome.